I installed Norton 360 on my iPhone and activated the VPN function. Some web sites I could reach before activating the VPN function became unavailable and returned the message "this web page is not available". Deactivating the VPN function allowed me to again reach the web site(s). Any help would be appreciated.
Many web sites do not allow access from known VPN IP addresses. They do this for copyright, legal, security, and political reasons. There is nothing a VPN provider can or should do to circumvent these legal protections. See this How to Geeks article. https://www.howtogeek.com/403771/why-do-some-websites-block-vpns/